Generally aligned with Trump on policy, but wary of Trumpism; often criticize the president sharply and publicly, particularly his anti-institutionalism and his policies and remarks on racial issues.
Prominent examples: Sen. Susan Collins of Maine, Rep. Will Hurd of Texas, Rep. Adam Kinzinger of Illinois, Sen. Lisa Murkowski of Alaska, Sen. Mitt Romney of Utah
Think of this group as the “very concerned” Republicans. They often verbally tsk-tsk about Trump, but then, say, vote for Brett Kavanaugh, irritating Democrats who want to see them marry their words with actions. This group is most important because they are likely to be the most forceful critics if, for example, Trump seems too chummy with Vladimir Putin. That occasional forcefulness makes this group different from the generally Pro-Trump bloc I described. And this strong criticism matters — Trump sometimes reverses himself in the face of it.
You might object to the term “moderate” here — Romney for example, is quite conservative on most policy issues. But being hostile to the media and at times to minorities is an important part of Trump’s political approach and increasingly that of the Republican Party’s. Being openly resistant to that drift in the party, like Romney, is a point of distinction between him and Republicans in the first two blocs.